Coating basic oxygen lance and method of coating

ABSTRACT

BUILDUP OF SLAG AND OTHER MATERIAL ON THE LANCE OF A BASIC OXYGEN FURNACE IS PREVENTED BY COATING THE LANCE PRIOR TO USE WITH A COMPOSITION COMPRISING FINELY DIVIDED INORGANIC PARTICULATE MATTER EMBEDDED IN AN OLEAGINOUS CARRIER.

United States Patent Office 3,575,706 COATING BASIC OXYGEN LANCE AND METHOD OF COATING Richard L. Ummel, Park Forest, 11]., assignor to Shell Oil Company, New York, N.Y. No Drawing. Filed May 6, 1968, Ser. No. 728,103

Int. 'Cl. B44c 1/06; C21c 5/32 US. Cl. 117-18 Claims ABSTRACT OF THE DISCLOSURE Buildup of slag and other material on the lance of a basic oxygen furnace is prevented by coating the lance prior to use with a composition comprising finely divided inorganic particulate matter embedded in an oleaginous carrier.

This invention relates to a method of treating the lance of a basic oxygen furnace to prevent skull formation thereon and to a basic oxygen furnace lance substrate having an improved coating thereon.

During the past fifteen to twenty years, the basic oxygen furnace has come into prominence in the use of steel making. The process involved, sometimes called the Linz- Donawitz process, basically requires the placing of the raw materials along with a proper amount of flux into the bottom of the furnace and then inserting through the top a lance through which oxygen is blown, thereby causing the reaction between the raw materials and the flux to take place forming a refined steel. The lance projecting down through the top of the furnace is watercooled, however, intense heats of from 2,000-3,000 F. often build up within the furnace. Slag and other materials often come in contact with the lance, adhering thereto, and if ignored will become so thickly coated on the lance that it cannot be Withdrawn back through the top of the furnace thereby requiring a shutdown.

The slag adhering to the lance is termed skull and is very detrimental to the steel making process. It inhibits efiicient functioning and, therefore, requires removal from the lance. This removal cannot be easily accomplished and often requires the use of oxy-acetylene cutting torches and various other time consuming and expensive" procedures. It is, therefore, apparent that this skull buildup not only is expensive in terms of inefficient operation and shutdown time, but requires extra personnel in order to remove the skull formation. -It hasnowbeen found that the buildup of skull on the lance of the basic oxygen furnace can be materially reduced or prevented by applying to the lance a coating of an oleaginous composition containing finely divided inorganic particulate matter. This coating, when applied to the lance, permits the lance to be inserted into the furnace for the steel making operation and for the lance to be withdrawn back through the top of the furnace with little or no skull formation adhering to the lance. This invention, therefore, has the obvious advantages of substantially limiting or preventing skull formation on the lance thereby making the process more efiicient and requiring less personnel to operate the steel making proce'ss. The time and labor consuming operations conventionally required to remove skull formations are substantially reduced or no longer required.

While it is not known with certainty the method by which this invention operates to prevent the skull buildup, it is theorized that the oleaginous carrier is burned off Patented Apr. 20, 1971 due to the intense heat within the burner leaving a coating of particular inorganic matter on the surfaces of the lance. This matter, when contacted with the hot molten skull, prevents the skull from adhering to the sides of the lance. However, it may also be that the oleaginous earner, under intense heat, polymerizes and forms materials which are helpful in the adherence of the particulate inorganic matter to the lance. Moreover, it is also possible that the oleaginous material is carbonized thereby leaving a soft carbon residue and particulate inorganic matter coating adhering to the outer surfaces of the lance which both assist in preventing skull from adhering to its surfaces.

The particulate inorganic matter to be used must be stable at the high temperatures found in the furnace during the steel making operation and not vaporize, melt off from or be fused to the lance. While any inorganic particulate matter having a sufficiently high melting or vaporization point may be used, it is preferred to employ refractory-type materials such as silica, alumina and derivatives thereof, zeolites (both natural and synthetic), clays, fullers earth, etc. The above inorganic materials may be used as such or may be chemically or physically altered as by treatment with a surfactant such as by basic exchange reaction with an amine or an amino amide. It is essential that the inorganic materials be finely divided in order that they may be evenly dispersed throughout the oleaginous carrier and so that they may adequately adhere to the surfaces of the oxygen lance. In general, particle sizes passing through a US. Standard No. 50 sieve are suitable.

The content of inorganic particulate matter in the oleaginous carrier will be dependent upon the application desired and is somewhat dependent upon the particular inorganic materials used. For some applications, amounts as low as 1% by weight of the inorganic material are sufficient, while compositions containing just enough oleaginous carrier to form a composition having a paste-like consistency which may be coated on the lance may best be suited for other applications. Compositions containing 5-50% of particulate inorganic matter and from 50% of oleaginous carrier are preferred.

The amount of coating material applied to the lance will depend upon the oleaginous carrier and the amount of particulate inorganic material used. In general the higher the inorganic content, the thinner the coating may be. The minimum coating should be at least 1 millimeter thick, while the maximum coating is dictated by process economics.

Various types of oleaginous carriers may also be used according to the invention. Mineral oils are particularly preferred because of availability and the ease of mixing with the inorganic material. Especially preferred types of inorganic particulate matter used are those conventionally used in the thickening of mineral oils to form greases, and therefore, upon the addition of only minor amounts of the inorganic material, the mineral oil carrier will generally thicken into a grease-like consistency. Because of ease of application and handling, mineral oil carriers are usually preferred; however, other types of carriers may be employed such as petroleum waxes which may be heated above their melting point, mixed with the inorganic material and then solidified. These can then be remelted and applied in a molten or liquid form onto the oxygen lance prior to its descent into the furnace. Other types of oleaginous materials which may be used are oilsoluble polymers and resins such as copolymers of ethylene and vinyl acetate or ethylene and esters of acrylic and methacrylic acids. Also copolymers of ethylene and propylene and homopolymers such as polyethylene, polypropylene and polystyrene may be used.

The coating compositions may be applied to the oxygen lance in numerous ways depending upon the physical characteristics of the coating composition. For compositions having low viscosity, a spraying device may be used. For compositions having a grease-like or gel consistency, the compositions can be spread on by hand or by mechanical device through which the lance would pass prior to entering the furnace. Solid compositions such as waxes or copolymers, can be molded into the shape of a lance and applied in solid form or could be melted and applied as a liquid. The method of application of the coating is not critical. What is important is that sufficient inorganic material be contained within the coating composition to adequately prevent the skull formation on the lance.

The invention will now be illustrated but not limited by the following examples.

EXAMPLE I An uncoated, water-cooled oxygen lance is inserted into the top of a basic oxygen furnace under normal operating conditions and oxygen blown through the lance during a normal steel making cycle for about 20 minutes at which time the lance is withdrawn from the furnace. On examination, the lance contains a coating of slag-like materials which coating is about 1-3 inches thick.

On subsequent heats this slag formation (skull) continues to buildup to massive proportions unless periodically removed.

EXAMPLE II A mineral oil is gelled to grease consistency by the addition of about 5% by weight of montmorillonite clay. The lance is then inserted into a basic oxygen furnace and used in the same maner as in Example I. At the end of the cycle, the lance is withdrawn from the furnace and examined and found to be substantially free of slag-like materials adhering to the lance.

EXAMPLE III A mineral oil gelled to grease consistency by the addition of about 25% by weight of the montmorillonite clay of Example [I is used to coat the oxygen lance and the procedure followed in 'Example I is again carried out. At the end of the cycle, the oxygen lance is withdrawn from the furnace and found to be entirely free of slag formation adhering to the lance.

EXAMPLE IV The following compositions are illustrative of other coating formulations which are also useful in the present invention.

TABIJE Inorganic material: Percent Weight Alumina 20 Fullers earth 28 Synthetics zeolite Aluminum silicate 22 Hectorite clay 34 Hectorite clay 26 Silica 40 Oleaginous carrier: 7 V U Mineral oil Paraffin wax 72 Mineral oil Mineral oil 78 Polyethylene 66 Ethylene-vinyl acetate copolymer 74 Mineral oil 60 The above compositions all perform satisfactorily as coatings for the oxygen lance. At the end of the steel making cycle the lance in each occasion is substantially free of slag or skull formation.

Other obvious modifications of this invention may be made without limiting the scope thereof and from this disclosure would be obvious to one having ordinary skill in the art.

I claim as my invention:

1. A method for preventing the buildup of slag and other materials on a water cooled lance of a basic oxygen furnace which comprises applying to the lance, prior to insertion into the furnace, a grease-like, non-rigid coating comprising finely divided particulate inorganic matter embedded in an oleaginous carrier.

2. The method of claim 1 wherein the oleaginous carrier is selected from the group consisting of mineral oils and petroleum waxes.

3. The method according to claim 1 wherein the finely divided inorganic particulate matter is a refractory material.

4. The method according to claim 3 wherein the oleaginous carrier is a mineral oil.

5. The method according to claim 3 wherein the refractory material is a day.

6. A water cooled oxygen lance coated with a greaselike, non-rigid coating material comprising finely divided inorganic particulate matter embedded in an oleaginous carrier.

7. The oxygen lance of claim 6 wherein the oleaginous carrier is selected from the group consisting of mineral oils and petroleum waxes.

8. The oxygen lance of claim 6 wherein the finely divided inorganic particulate matter is a refractory material.

9. The oxygen lance of claim 8 wherein the oleaginous carrier is a mineral oil.

10. The oxygen lance of claim 8 wherein the refractory material is a clay.

References Cited UNITED STATES PATENTS 2,546,937 3/1951 Wyandt et al 7560X 3,058,823 10/1962 Churcher 75-60 3,230,056 1/1966 Arant et al 117-5.3X

3,467,542 9/ 1969 Nordlie 117-94 FOREIGN PATENTS 245,529 6/ 1963 Australia 26634.l

ALFRED L. LEAVITI, Primary Examiner J. H. NEWSOME, Assistant Examiner U.S. Cl. X.R. 11727, 94; 266-34 

